In the Marlin M. Hanson, et al, U.S. Pat. No. 4,012,724 there is disclosed an optical page composer that is comprised of a magnetizable film layer in which single wall domains or bubble domains may be sustained and moved about and to which are inductively coupled a slotted digit drive line and perpendicular slotted word drive line, the intersection of which forms four quadrants that define or are defined by a memory area in the bubble domain supporting layer. An opaque shield is oriented in the memory area for optically shielding a bubble domain except when in the first quadrant within the memory area. Coincident current selection, e.g., concurrent half-current selection, of the digit drive line and of the word drive line by half-select signals of the proper polarity permits the one fully selected memory area to be selected for the selective writing of a "1" or of a "0" therein, e.g., the associated bubble domain is selectively positioned on either the first or the third quadrants.
The optical page composer is preferably comprised of a magnetizable film layer of, e.g., garnet, having orthogonal sets of parallel slotted digit drive lines and parallel slotted word drive lines, each intersection of which forms four quadrants that define or are defined by an associated memory area with an opaque shield oriented in three of the four quadrants of each memory area. In the operation of such page composer, as during the writing or transferring operation, it has been observed that the bubble domains, under certain operating conditions, may escape from their proper stable conditions, e.g., the first quadrant, within the memory area, or, alternatively, may become "stuck" in one stable position and may not be selectively positioned from one stable position, e.g., the first quadrant into another stable position, e.g., the third quadrant. The present invention is directed toward a method of ensuring the reliable operation of such Marlin M. Hanson, et al, U.S. Pat. No. 4,012,724 including forming the slotted drive lines within, e.g., ion milled channels that are formed in the surface of the bubble domain supporting layer.